Police are expected this week to wrap up their investigation into claims that the energy secretary, Chris Huhne, asked his wife to take penalty points for speeding.

A file will be handed to the Crown Prosecution Service amid reports that the two key witnesses gave terse evidence under oath.

Huhne has denied throughout the last month claims brought by his ex-wife, Vicky Pryce, that he persuaded her to take three points on his behalf – a criminal offence. She alleged Huhne incurred points for speeding on the night of 12 March 2003 when heading down the M11 from Stansted to London after arriving on a plane from Brussels, where he worked as an MEP.

It has been alleged that, since Huhne had incurred points previously, he offloaded the new points on to Pryce to avoid losing his driving licence.

Pryce was attending a dinner at the London School of Economics (LSE) that night, so the investigation turns on whether she left London with enough time to be driving the car from the airport back down to London and incur the points herself at 11.20pm.

The Essex police investigation is reported to have stretched to officers contacting guests who were at the same LSE dinner.

Huhne and Pryce were separately interviewed by police last week. Reports have emerged that neither was particularly helpful.

Huhne is said to have given terse answers, exercising his right to say "no comment" to much of the questioning, while persistent reports suggest Pryce, who brought the allegation into the public domain, subsequently decided to refuse to repeat the claims. One Sunday newspaper said Pryce refused to do so because her children feared she could be charged with conspiracy to pervert the course of justice, and possibly be sent to prison.

Sources close to Pryce said she was "extremely irritated" by suggestions she was unwilling fully to co-operate with investigators. Her lawyer Sarah Webb, said: "Vicky Pryce continues to co-operate with the police, as Chris Huhne MP has indicated he does."

Huhne is believed to have become convinced his wife did not intend the situation to get as serious as a formal court case, and that she wanted merely to "wound not kill".

Friends of the pair have been engaged in a strenuous attempt to broker a truce, attempting to ameliorate the damage to the family. One of the couple's children is doing his A-levels.

The pair have been embroiled in the high-profile disagreement since Huhne left his wife of 27 years for Carina Trimingham, who ran his campaign to become leader of the Liberal Democrats, which he lost to Nick Clegg.

Pryce, who immediately filed for divorce, denies floating the suggestion that Huhne passed the speeding points on to her. One friend said: "Vicky is dismayed by suggestions that the speeding affair started because she was seeking revenge. She was not the one to raise it."

One newspaper reported on Monday that the director of prosecutions, Keir Starmer, could personally consider the case because it is so sensitive.